QUOTE(davm88 @ May 18 2007, 03:57 PM)

QUOTE(englisher @ May 18 2007, 03:07 PM)

QUOTE(weerydo @ May 17 2007, 08:45 PM)

thts wot i thot m8, and i am still sure i am. maybe many ppl didnt reed it correctly and they just red constant and thot constand speed so a set amount less than 700n. so any1 else got any views on this? its question 3 of multi choice

The first post on this page I went through it very clearly!!

QUOTE(davm88 @ May 18 2007, 01:33 PM)

hey, are these solutions accurate or just sumbodies answers? im still sticking to my guns about 3 being D, but want to know other peoples views on this.

See the first post on the top of this page!!!

i know, but i stil dnt understand. can u see where im comin from tho? tht this lift IS gettin faster and faster, and that the guy inside will EVENTUALLY get weightless?

Just think of the equations. If he was going infinitely fast, at a constant speed, it would be precisely the same for him as if he was going at zero velocity. The upward force would equal the downward force so there would be no unbalanced force. Therefore, he wouldn't ever get weightless travelling at a constant speed. Surely then at every speed up to that point he would not become "weightless"? That doesn't quite answer your question so I'll go through the first post again.

W = 700N

Force upwards from floor of lift (balanced by force on the scales pushing up) = "S"

He is

**accelerating** downwards, there must be an unbalanced force, so Weight is greater than S (down greater than up). Accelerating at a constant rate, so "a" is constant. For the purposes of illustration, constant1 = a constant 2 =m

a = F(un)/m

constant1 = F(un)/constant2

Therefore, F(un) = constant1 x constant2

Unbalanced force is constant

Do you follow up to this point?

Unbalanced force = Weight - "S" (Remember how weight was greater?)

S = Weight - unbalanced force

= 700 - constant

= a constant less than 700N

Hope you get it now.